Abstract

Supernova explosions in a cloudy interstellar medium produce a
three-component medium in which a large fraction of the volume is filled
with hot, tenuous gas. In the disk of the galaxy the evolution of
supernova remnants is altered by evaporation of cool clouds embedded in
the hot medium. Radiative losses are enhanced by the resulting increase
in density and by radiation from the conductive interfaces between
clouds and hot gas. Mass balance (cloud evaporation rate = dense shell
formation rate) and energy balance (supernova shock input = radiation
loss) determine the density and temperature of the hot medium. A
self-consistent model of the interstellar medium developed herein
accounts for the observed pressure of interstellar clouds, the galactic
soft X-ray background, the O VI absorption line observations, the
ionization and heating of much of the interstellar medium, and the
motions of the clouds.